Field of the Invention
The present invention relates to a sheet conveyance apparatus, an image forming apparatus, and an image forming system.
Description of the Related Art
There has been used an interleaf inserting apparatus which inserts interleaves, such as thick paper or colored paper (including a front cover sheet and a back cover sheet) into sheets on which an image is formed by an image forming apparatus. Sheet-feeding in the interleaf inserting apparatus includes two steps of primary sheet-feeding conveyance in which interleaves loaded on a loading unit are picked up and conveyed to a resist part, and secondary sheet-feeding conveyance in which the interleaves are conveyed from the resist part to a merging point with image-formed sheets. In the primary sheet-feeding conveyance, the interleaves on the loading unit need to be separated one by one by a separating roller or the like, and the time required for the primary sheet-feeding conveyance greatly varies according to the loading amount of the interleaves, the abrasion degree of the separating roller, and the like. Thus, the primary sheet-feeding conveyance is temporally unstable. The timing to start the primary sheet-feeding conveyance has been gradually advanced in order to ensure the productivity during the interleaves are inserted, and the primary sheet-feeding conveyance is controlled to be started before the actual insertion timing at the point when the insertion of the next interleaf is determined. In other words, in order to merge the interleaves with the image-formed sheets in a stable state, it is desired to complete the primary sheet-feeding conveyance as soon as possible. For example, the primary sheet-feeding conveyance can be advanced crossing jobs by completing the primary sheet-feeding conveyance of the interleaf to be used in the next job although the preceding job has not been terminated.
Furthermore, normally, when interleaves are inserted to a discharging path of the image-formed sheets from another path and a jam occurs during feeding an interleaf, the operation of the image forming apparatus has been forcibly stopped. Thus, the remaining sheets in the image forming apparatus need to be removed, and the operability has been poor. Accordingly, in order to reduce the remaining sheets in the image forming apparatus, there has been proposed an image forming apparatus which discharges the fed sheets in the apparatus after performing image forming processing without immediately stopping the apparatus when a jam occurs during feeding an interleaf (see JP 2003-280305 A). In other words, by continuing the operation to the sheets remaining inside the apparatus when the jam occurs, the efficiency of the operation at the time of recovery (recovery from the jam) is improved.
However, as described above, when primary sheet-feeding conveyance in an interleaf inserting apparatus is advanced and a jam occurs in the primary sheet-feeding conveyance, sheets before the order, in which the interleaf causing the jam is supposed to be inserted, have not been fed. In other words, the sheet-feeding and the conveyance of the sheets to be discharged before the uninserted interleaf have been suspended. In this case, the recovery needs to be performed from the sheets before the interleaf causing the jam in the order, and which has caused a problem that the productivity and the work efficiency when jobs are successively performed is reduced.
FIG. 17 illustrates an example of conventional sheet conveying control. In FIG. 17, an interleaf to be inserted as a front cover sheet of the k-th job (job k) is indicated as “Pk-front”. A sheet on which the m-th image of the k-th job is to be formed is indicated as “Qk-m”. An interleaf conveying path is a path to convey interleaves to be inserted, an image-forming-sheet conveying path is a path to convey sheets on which an image is to be formed, and a merged conveying path is a sheet conveying path after a merging point which is the sheets on which an image is to be formed and the interleaves are merged. The abscissa indicates time.
Here, it is assumed that it is instructed to discharge four sheets to form an image (image forming sheets), which sheets are to be discharged after a front cover sheet (interleaf) is discharged in the job 1, and to discharge an image forming sheet which is a sheet to be discharged after a front cover sheet (interleaf) is discharged in the job 2. When the sheets until the third image forming sheet of the job 1 have been fed at the point when a jam is detected during primary sheet-feeding conveyance of the front cover sheet of the job 2, the fourth image forming sheet of the job 1 has not been fed but the sheet-feeding is stopped. As a result, at the point when the sheets until the third image forming sheet of the job 1 have been conveyed following the front cover sheet of the job 1, the job is suspended. In other words, although the jam is caused by a sheet (interleaf) of the job 2, the job 1 is suspended in the middle, and the recovery needs to be performed from the fourth image forming sheet of the job 1. Thus, the productivity and work efficiency at recovery have been poor.